1. Field of the Invention
Embodiments described herein relate generally to a charged particle beam writing apparatus and a charged particle beam writing method, and for example, relate to a division method of a stripe region for writing.
2. Related Art
A lithography technique which takes a part of the development of miniaturization of semiconductor devices is, among semiconductor manufacturing processes, an extremely important process as the only process to generate a pattern. In recent years, with the high integration of an LSI, circuit line heights required for semiconductor devices are miniaturized year by year. In order to form desired circuit patterns on the semiconductor devices, precise original patterns (also referred to as reticles or masks) are required. In this case, an electron beam writing technique has an essentially excellent resolution, and is used in production of precise original patterns.
FIG. 12 is a conceptual diagram for explaining an operation of a variable-shaped electron beam writing apparatus.
The variable-shaped electron beam (EB: Electron beam) writing apparatus operates as follows. An oblong opening 411 to shape an electron beam 330 is formed in a first aperture plate 410. A variable-shaped opening 421 to shape the electron beam 330 having passed through the opening 411 of the first aperture plate 410 into a desired oblong shape is formed in a second aperture plate 420. The electron beam 330 irradiated from a charged particle source 430 and having passed through the opening 411 of the first aperture plate 410 is deflected by a deflector and passes through a part of the variable-shaped opening 421 of the second aperture plate 420 such that a target object 340 placed on a stage continuously moving in one predetermined direction (for example, an X direction) is irradiated with the electron beam 330. That is, an oblong shape which can pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 is written in a write region of the target object 340 placed on the stage continuously moving in the X direction. A scheme which causes an electron beam to pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 to form an arbitrary shape is called a variable-shaping scheme (VSB scheme).
A writing apparatus divides a write region into stripe regions in a thin rectangular shape of a fixed height (see Published Unexamined Japanese Patent Application No. 2010-267844, for example). Then, each stripe region is divided into a plurality of data processing regions in a direction perpendicular to the direction in which the write region is divided into the stripe regions to perform data processing in units of data processing regions. The division size of the data processing region is set such that the number of beam shots in the region becomes uniform to prevent a delay of write processing. If a portion of a cell is contained in a data processing region, the cell is allocated to the data processing region. Thus, if a cell extends over a plurality of data processing regions, the same cell is allocated to the plurality of data processing regions.
When a write region of a target object such as a mask is divided into the above stripe regions, the height of the last stripe may become extremely smaller than the height of other stripe regions. In other words, the last stripe will have a remaining height dimension after the write region being successively divided. If, in such a case, the last stripe is divided into data processing regions such that the number of beam shots becomes approximately uniform, the height of data processing regions in the last stripe will be larger than the height in other stripe regions. That is, the last stripe will be an elongated data processing region. Thus, if a portion of a cell is contained in a data processing region of the last stripe, the number of the cells will be comparatively larger than the number of cells contained in data processing regions of other stripe regions. Thus, a problem of a longer time of processing needed to determine whether a cell belongs to the data processing region of the last stripe is posed. As a result, a problem that a calculation time when a pattern density or the like in the data processing region of the last stripe is calculated is delayed when compared with data processing regions of other stripe regions is posed.